The overall goal of this project is the isolation and characterization of the gene coding for blood coagulation factor IX. Information will also be sought regarding the control of factor IX synthesis in hepatocytes. Poly A+ messenger RNA will be isolated from human and canine liver and a complementary DNA (cDNA) bank will be synthesized from the isolated messenger RNA using reverse transcriptase. Double stranded cDNA will be then obtained using DNA polymerase I. Restriction endonucleases and terminal transferase will be bused to insert cDNA fragments into a plasmid (pBR 322). DNA coding for gactor IX will be identified either by using a specific primer based upon consideration of the primary sequence information available on human and canine factor IX and/or by identifying factor IX synthesized in in vitro systems with factor IX-specific antibodies. The genomic factor IX gene will be identified and isolated from a genomic library of human DNA using the cDNA obtained above as a prove. This same approach willbe used for the canine system. The nucleotide sequence for human and canine factor IX cDNA will be determined as will that genomic DNA coding for factor IX synthesis. Genomic DNA will also be examined from the various classes of hemophilia b patients and from dogs with hemophilia b. The information concerning the nucleotide sequence of the genomic DNA coding for factor IX will facilitate the elucidation of te molecular defect in hemophilia b. The results from these experiments will also open new avenues of investigation concerning the relationship between structure and function in factor IX as well as providing the development of new modes of treatment of hemophilia b.